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"Because of their bravery, and the bravery of other agents around the world, our ministers very often play their cards knowing at least some of what is in the other side's hand, which improves their ability to deliver a world based on rules, stability and democracy."

The head of MI6 again made a pitch for Russians to work against the Kremlin, declaring "Putin is not Russia".

He said in a speech in Istanbul: "I must be clear that my Government, my Service and myself are not hostile to Russia, only to the actions of the Kremlin. While Putin deceives and dissembles, our task is to illuminate the truth.

"Putin is not Russia. And not all Russians subscribe to Putinism. Some keep their heads down and try to get on with their lives as best they can. Some, like Alexei Navalny, resist openly, and die for their beliefs. But others do so secretly, by working with MI6.

"Intelligence officers immerse themselves in the cultures of their interlocutors. Russia is, in many ways, a big part of the history of MI6. The country holds a special place within the service.

"MI6 is full of men and women who know and love many of the achievements of Russian culture, and who understand and respect the sacrifices of its people in our shared struggle against Nazi Germany.

"To those men and women in Russia who have truths to share and the courage to share them, I invite you to contact MI6. You will be working to bring peace to our continent; to protect the long-term interests - and redeem the honour - of your country.

"You will be working with a world class organisation. We will do everything in our power to keep you safe. Your needs and aspirations will be paramount. We can help you make a difference."

Intelligence officers will, for the first time, create a portal on the dark web used by criminals and dissidents trying to hide their identities.

And security chiefs hope this will allow the UK to recruit more spies to hand over sensitive information linked to Russian, Chinese, Iranian or terrorist activity.

It is far harder for intelligence agencies and police forces to detect and intercept messages and information shared on the dark web, illustrating why it is so popular for organised crime networks.

It marks another significant shift in the World of espionage, with fears intensifying that Russian intelligence agencies are relying on a "gig economy"-style recruitment method of paying criminals for sabotage, kidnapping and arson conspiracies.

And Sir Richard said Putin could have faced a political crisis "that threatens his own rule" had North Korea, Iran and China not supported the Russian military.

MI6 chief issues plea to Russians as he reveals how Vladimir Putin clinging on